function regAudioAndVideo(content) {
    /* 提取标签后,再用自定义内容组合
     * var str="<audio alt='asd' src='aa.mp4'></audio>飒飒<audio alt='yui' src='trgh.wav'>456</audio>12<video asd='asd' src='asd.mp3' aa></video><video fsd='sd' src='a22d.mp3' d3>sd</video>"
     * regAudioAndVideo(str)
    */
    var regAudio = /(<audio)(.*?audio>)?/ig;
    content = content.replace(regAudio, '$1 class="regvideo" controls="" $2');
    var regVideo = /(<video)(.*?video>)?/ig;
    content = content.replace(regVideo, '$1 class="regvideo" controls="" $2');
    return content;
}